The long-term goal of this project is to understand the mechanism by which 4-hydroxyalkenals and related aldehydes are detoxified by the heart and to assess their contribution to myocardial oxidative injury. These aldehydes are generated by endogenous lipid peroxidation during metabolism of anticarcinogens, food products and industrial and environmental pollutants. However, the cardiac metabolism of these aldehydes and their contribution to free radical injury are not well understood. Our hypothesis is that aldose reductase-catalyzed reduction constitutes the major pathway for the detoxification of these aldehydes in the heart. In association with glutathione conjugation, this pathway minimizes oxidative injury by promoting the detoxification of unsaturated aldehydes. The aim of the proposed studies is to understand the role of aldose reductase in detoxifying unsaturated aldehydes and to identify the contribution of this detoxification pathway to cardiac antioxidant defenses. For these studies, aldose reductase will be purified to homogeneity from human heart and its catalytic efficacy in reducing hydroxyalkenals, related aldehydes and their glutathione adducts will be examined. For most metabolic studies 4-hydroxy-2-trans nonenal (HNE) will be used as a model unsaturated aldehyde. We will identify the major cellular metabolites of HNE isolated rat ventricular myocytes and assess the relative contribution of aldose reductase to HNE metabolism. In order to examine the efficiency of this enzyme in promoting HNE metabolism and minimizing its toxicity, the effects of inhibiting aldose reductase on HNE-induced myocyte hypercontracture and ATP depletion will be studied. During whole-cell patch-clamp, myocytes will be supplemented with aldose reductase to assess the role of this enzyme in attenuating the effects of HNE. In order to assess the, significance of aldose reductase- catalyzed reduction of HNE to cardiac oxidative injury we will examine the effects of aldose reductase inhibitors on the reperfusion injury to isolated perfused rat hearts. These studies will provide insights into the metabolic processes by which the heart detoxifies reactive aldehydes and help in understanding the role of these aldehydes as mediators of oxidative injury.